I. Field of the Invention
This invention relates generally to apparatus for repairing and refurbishing the bearing surfaces of rotating shafts of large machines at a job site, and more particularly to a portable journal turning lathe that can be readily transported to a location in the field where a machine to be repaired is located, assembled in place on the machine's shaft to be turned, and then operated to remove any scoring and other surface irregularities from the shaft so that it is ready for replacement of its bearings.
II. Discussion of the Prior Art
In the past, when it has become necessary to refurbish the journal area on a shaft of large machines such as rock crushers, ship's rudders, etc., it has been necessary to tear down the machine and ship the assembly, including the shaft, to a machine shop where it may be turned on an engine lathe typically weighing 90 tons or more. This necessarily increases the down time of the machine being refurbished. Thus, a need exists for a portable journal turning lathe that can be taken to the job site in easily transportable parts and then assembled onto a shaft to be turned, quickly and easily. Such a lathe must still provide close tolerance machining of a shaft, equivalent to that which can be obtained using a conventional engine lathe.
In my earlier U.S. Pat. No. 4,739,685, I describe a split frame portable machining lathe comprising a clam shell member having a stationary clamping ring adapted for concentric mounting on a pipe to be machined and a rotatable ring gear journaled for rotation on the stationary clamping ring. Affixed to the rotatable ring gear is a cutting tool feed mechanism which can be used to advance a cutting tool in the radial direction to thereby control the depth of cut as the cutting tool carried by the feed mechanism moves in an orbital path about the pipe or shaft being turned.
The device disclosed in my U.S. Pat. No. 4,739,685 is intended primarily for accurately cutting off the end of a pipe in that there is no provision for longitudinal displacement of the cutting tool holder. In another of my earlier patents U.S. Pat. No. 5,189,933, I have disclosed yet another machine for treating the end portion of a pipe. Again, a clam shell mechanism is employed for supporting a tool carrier and rotating same about the periphery of the pipe on which the clam shell member is assembled. The tool carrier provides for only limited longitudinal or axial displacement of the tool bit along with radial displacement, but has been found that the device of the '933 patent cannot maintain accurate tolerances over much more than about 2-3 inches in the axial direction.
Therefore, a need exists for a journal turning lathe that can be readily transported in a disassembled state to a job site and then assembled onto the shaft to be turned quickly and easily and which can accurately maintain a predetermined tolerance of 5/10000 of an inch or better over an axial length from a few inches up to two feet or more.